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19 pages, 3415 KiB

Open AccessArticle

Dynamic Modeling of Heat-Integrated Air Separation Column Based on Nonlinear Wave Theory and Mass Transfer Mechanism

by Hang Zhou, Xinlei Xia and Lin Cong

Processes 2025, 13(4), 1052; https://doi.org/10.3390/pr13041052 - 1 Apr 2025

Viewed by 270

Abstract

The air separation process is an important industrial process for the production of high-purity nitrogen and oxygen, representing the level of technological development in a country’s chemical industry. It has high energy consumption but very low energy utilization efficiency. In the overall environment [...] Read more.

The air separation process is an important industrial process for the production of high-purity nitrogen and oxygen, representing the level of technological development in a country’s chemical industry. It has high energy consumption but very low energy utilization efficiency. In the overall environment of increasingly scarce global energy, the application of internal heat coupling technology in the air separation process can effectively reduce energy consumption. However, due to the low-temperature characteristics, ultra-high purity characteristics, and the nature of multi-component systems of the heat-integrated air separation column (HIASC), its modeling process and dynamic characteristic analysis are complex. To solve the disadvantages of overly complex mechanistic models and insufficient accuracy of traditional simplified models, a concentration distribution curve description method based on the mass transfer mechanism is proposed, and combined with the traditional wave theory, a nonlinear wave model of the HIASC is established. Based on this model, static and dynamic analyses were carried out, and the research results prove that the newly established nonlinear wave model maintains high accuracy while simplifying the model complexity. It can not only accurately track the concentration changes of key products but also fully reflect various typical nonlinear characteristics of the system. Compared to the mechanism model, the wave model can reduce the running time by approximately 20%, thereby improving operational efficiency. This method explains various characteristics of the system from a perspective different from that of the mechanistic model. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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12 pages, 6681 KiB

Open AccessArticle

An Investigation of the Heating Performance of a Groundwater-Based Air Conditioning System for an Agricultural Greenhouse

by Koji Toriyama, Kyosuke Wakishima, Ichiei Kuranuki, Shigeru Tada and Shumpei Funatani

Processes 2025, 13(3), 778; https://doi.org/10.3390/pr13030778 - 7 Mar 2025

Viewed by 753

Abstract

Food shortages due to the decreasing arable land area, which is a consequence of the increasing global population, have brought greater attention to greenhouses. However, the cost of air conditioning in greenhouses is high. Therefore, in this study, the heating performance of a [...] Read more.

Food shortages due to the decreasing arable land area, which is a consequence of the increasing global population, have brought greater attention to greenhouses. However, the cost of air conditioning in greenhouses is high. Therefore, in this study, the heating performance of a low-running-cost air conditioning system using groundwater was evaluated in winter in an agricultural greenhouse. The system consisted of a temperature control room in an agricultural greenhouse and a groundwater recirculation system. The pumped groundwater was passed through a polytube heat exchanger panel and stored in a recirculation tank. The stored water circulated back to the heat exchanger to create a water recirculation system. When operated with only a single 250 L recirculation tank, the temperature in the temperature control room was maintained at 4.9–19.4 °C, even when the maximum and minimum outdoor air temperatures were 12.6 and −2.3 °C, respectively. To achieve a higher minimum temperature in the temperature control room, a method was developed to enable the system to switch from the recirculating water to flowing groundwater when the recirculating water temperature fell below the groundwater temperature. Consequently, the minimum temperature in the temperature control room could be maintained at 8.0 °C. In an experiment in which the capacity of the recirculation tank was tripled (750 L), the minimum temperature was maintained at 7.9 °C, which is a stable temperature for cucumber cultivation. These results indicate that the heating capacity of the proposed system is equivalent to that of ACCFHES (An aquifer coupled cavity flow heat exchanger system) and other heating systems for winter heating. Therefore, this proposed method makes it possible to cultivate plants that grow in a climate similar to that of cucumbers at a low running cost. The amount of heating capacity that could be extracted simply by circulating groundwater was also revealed. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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20 pages, 3339 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Experimental Dielectric Properties and Temperature Measurement Analysis to Assess the Thermal Distribution of a Multimode Microwave-Assisted Susceptor Fixed-Bed Reactor

by Alejandro Fresneda-Cruz, Gonzalo Murillo-Ciordia and Ignacio Julian

Processes 2025, 13(3), 774; https://doi.org/10.3390/pr13030774 - 7 Mar 2025

Viewed by 538

Abstract

In this study, the integration of microwave-assisted technology into fixed-bed configuration processes is explored aiming to characterize and address its challenges with a customized multimodal microwave cavity. This research focuses on evaluating the uncertainty in contactless temperature measurement methods as spectral thermographic cameras [...] Read more.

In this study, the integration of microwave-assisted technology into fixed-bed configuration processes is explored aiming to characterize and address its challenges with a customized multimodal microwave cavity. This research focuses on evaluating the uncertainty in contactless temperature measurement methods as spectral thermographic cameras and infrared pyrometers, microwave heating performance, and the thermal homogeneity within fixed beds containing microwave–susceptor materials, including the temperature-dependent dielectric characterization of such materials, having different geometry and size (from 120 to 5000 microns). The thermal inhomogeneities along different bed configurations were quantified, assessing the most appropriate fixed-bed arrangement and size limitation at the employed irradiation frequency (2.45 GHz) to tackle microwave-assisted gas–solid chemical conversions. An increased temperature heterogeneity along the axial profile was found for finer susceptor particles, while the higher microwave susceptibility of coarser grades led to increased temperature gradients, ΔT > 300 °C. Moreover, results evidenced that the temperature measurement on the fixed-bed quartz reactor surface by a punctual infrared pyrometer entails a major error regarding the real temperature on the microwave susceptor surface within the tubular quartz reactor (up to 230% deviation). The experimental findings pave the way to assess the characteristics that microwave susceptors and fixed beds must perform to minimize thermal inhomogeneities and optimize the microwave-assisted coupling with solid–gas-phase reactor design and process upscaling using such multimode cavities. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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18 pages, 1588 KiB

Open AccessArticle

Root Cause Analysis for Observed Increased Sedimentation in a Commercial Residue Hydrocracker

by Ivelina Shishkova, Dicho Stratiev, Petko Kirov, Rosen Dinkov, Sotir Sotirov, Evdokia Sotirova, Veselina Bureva, Krassimir Atanassov, Vesislava Toteva, Svetlin Vasilev, Dobromir Yordanov, Radoslava Nikolova and Anife Veli

Processes 2025, 13(3), 674; https://doi.org/10.3390/pr13030674 - 27 Feb 2025

Cited by 1 | Viewed by 525

Abstract

Ebullated bed vacuum residue hydrocracking is a well-established technology providing a high conversion level of low-value residue fractions in high-value light fuels. The main challenge in this technology when processing vacuum residues derived from different crude oils is the sediment formation rate that [...] Read more.

Ebullated bed vacuum residue hydrocracking is a well-established technology providing a high conversion level of low-value residue fractions in high-value light fuels. The main challenge in this technology when processing vacuum residues derived from different crude oils is the sediment formation rate that leads to equipment fouling and cycle length shortening. With the severity enhancement, the asphaltenes become more aromatic and less soluble which leads to sediment formation when the difference between solubility parameters of asphaltenes and maltenes goes beyond a threshold value. Although theoretical models have been developed to predict asphaltene precipitation, the great diversity of oils makes it impossible to embrace the full complexity of oil chemistry by any theoretical model making it impractical for using it in all applications. The evaluation of process data of a commercial ebullated bed vacuum residue hydrocracker, properties of different feeds, and product streams by intercriteria and regression analyses enabled us to decipher the reason for hydrocracked oil sediment content rising from 0.06 to 1.15 wt.%. The ICrA identified the presence of statistically meaningful relations between the single variables, while the regression analysis revealed the combination of variables having a statistically meaningful effect on sediment formation rate. In this study, vacuum residues derived from 16 crude oils have been hydrocracked as blends, which also contain fluid catalytic cracking heavy cycle oil and slurry oil (SLO), in a commercial H-Oil plant. It was found that the hydrocracked oil sediment content decreased exponentially with fluid catalytic cracking slurry oil augmentation. It was also established that it increased with the magnification of resin and asphaltene and the reduction in sulfur contents in the H-Oil feed. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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25 pages, 5846 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Harvesting Salinity Gradient Energy by Diffusion of Ions, Liquid Water, and Water Vapor

by Joost Veerman

Processes 2025, 13(2), 554; https://doi.org/10.3390/pr13020554 - 16 Feb 2025

Viewed by 533

Abstract

In this paper, we briefly discuss the main points of salinity gradient energy (SGE). First, we discuss the sources of SGE and the methods to harvest it. Then, we calculate, using the laws of physical chemistry, the amount of energy that can be [...] Read more.

In this paper, we briefly discuss the main points of salinity gradient energy (SGE). First, we discuss the sources of SGE and the methods to harvest it. Then, we calculate, using the laws of physical chemistry, the amount of energy that can be harvested with three selected methods based on the diffusion of ions, liquid water, and water vapor, respectively. Then, we give an overview of the applications, highlighting a number of new developments such as assisted reverse electrodialysis (ARED) and energy storage. It turns out that reverse electrodialysis offers unexpected possibilities such as energy storage, utilizing waste heat, and the administration of transdermal drug delivery, a technique that has been launched very recently. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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19 pages, 7637 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Design of Ejectors for High-Temperature Heat Pumps Using Numerical Simulations

by Julian Unterluggauer, Adam Buruzs, Manuel Schieder, Verena Sulzgruber, Michael Lauermann and Christoph Reichl

Processes 2025, 13(1), 285; https://doi.org/10.3390/pr13010285 - 20 Jan 2025

Viewed by 993

Abstract

Decarbonization of industrial processes by using high-temperature heat pumps is one of the most important pillars towards sustainable energy goals. Most heat pumps are based on the standard Carnot cycle which includes an expansion valve leading to irreversible dissipation and energetic losses. Especially [...] Read more.

Decarbonization of industrial processes by using high-temperature heat pumps is one of the most important pillars towards sustainable energy goals. Most heat pumps are based on the standard Carnot cycle which includes an expansion valve leading to irreversible dissipation and energetic losses. Especially for high-temperature applications, these losses increase significantly, and a replacement of the conventional throttle valve with an ejector, which is an alternative expansion device, for partial recovery of some of the pressure lost during the expansion, is investigated in this paper. However, designing such a device is complicated as the flow inside is subject to multiphase and supersonic conditions. Therefore, this paper aims to streamline an approach for designing ejectors for high-temperature heat pumps using numerical simulations. To showcase the application of the design procedure, an ejector, which is used to upgrade a standard cycle high-temperature heat pump with the synthetic refrigerant R1233zdE, is developed. To design the ejector heat pump, an interaction between a fast 1D design tool, a 1D heat pump cycle simulation, and a 2D CFD simulation is proposed. An ejector is designed for a sink temperature of 130 °C, which can potentially increase the COP of the heat pump by around 20%. Preliminary measurements at off-design conditions at 100 °C sink temperature are used to validate the design procedure. The pressure distribution inside the ejector is well captured, with relative errors around 4%. However, the motive nozzle mass flow was underpredicted by around 30%. To summarize, the presented approach can be used for designing ejectors of high-temperature heat pumps, although the numerical modeling has to be further developed by validation with experiments to improve the prediction of the motive mass flow. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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19 pages, 3106 KiB

Open AccessArticle

Simultaneous Optimization of Hydrogen Network with Pressure Swing Absorption Based on Evolutionary Response Surface Method

by Lingjun Huang, Qingyu Zhu, Weiqi Sun, Dongyang Dou, Qili Wang and Guilian Liu

Processes 2025, 13(1), 261; https://doi.org/10.3390/pr13010261 - 17 Jan 2025

Viewed by 670

Abstract

The simultaneous optimization of complex process units and hydrogen networks is a significant challenge in refinery hydrogen network integration. To address this, an evolutionary response surface-based collaborative optimization method is proposed, enabling the concurrent optimization of pressure swing adsorption (PSA) and the hydrogen [...] Read more.

The simultaneous optimization of complex process units and hydrogen networks is a significant challenge in refinery hydrogen network integration. To address this, an evolutionary response surface-based collaborative optimization method is proposed, enabling the concurrent optimization of pressure swing adsorption (PSA) and the hydrogen network. This method develops a mechanistic model for PSA and alternates between random sampling and evolutionary response surface-based hydrogen network optimization to obtain diverse sampling points and potential optimal solutions. The PSA mechanistic model is then used to compute the accurate output parameters for the sampled points, and these parameters are incorporated into the hydrogen network optimization to obtain precise objective function values. An efficient optimization framework is presented to streamline the process. The proposed method is applied to a refinery hydrogen network integration case study, comprehensively considering both PSA costs and hydrogen utility costs. The results demonstrate that the method is computationally efficient and effectively reduces the refinery’s total annual costs. The accuracy of the optimization results is significantly improved compared to traditional methods, providing an effective solution for the collaborative optimization of the refinery hydrogen network and PSA. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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22 pages, 7560 KiB

Open AccessArticle

Study of the Transient Heat Transfer of a Single-U-Tube Ground Heat Exchanger by Integrating a Forward-Difference Numerical Scheme with an Analytical Technique

by Elias M. Salilih, Esa Dube Kerme, Alan S. Fung, Wey H. Leong and Walter D. Leon-Salas

Processes 2024, 12(12), 2867; https://doi.org/10.3390/pr12122867 - 14 Dec 2024

Viewed by 819

Abstract

This study presents the development of a novel computational technique for modeling the transient heat transfer in the outer and inner regions of a single U-tube ground heat exchanger. The modeling approach couples a forward-difference numerical technique with a well-established analytical method with [...] Read more.

This study presents the development of a novel computational technique for modeling the transient heat transfer in the outer and inner regions of a single U-tube ground heat exchanger. The modeling approach couples a forward-difference numerical technique with a well-established analytical method with the aim of reducing the two-dimensional axisymmetric heat transfer problem into a one-dimensional problem, which has the benefit of reducing the computational time. Furthermore, the suggested method is numerically stable compared to a full numerical scheme, and the solution converges for a time step of up to 150 min. This is because the suggested method computes the heat transfer of the streaming fluid in the U-tube, which has a lower thermal capacitance, using the analytical technique, resulting in numerical stability at a larger time step, while the full numerical scheme has stability issues at a large time step as it computes the heat transfer of the flowing fluid in the U-tube, which also requires more computational time than the suggested method. In this model, numerical and analytical analyses are coupled with borehole wall temperature. The time-varying temperature histories of the grout material inside the borehole, the borehole wall, and the surrounding soil are presented. In addition, the time variations in the exit fluid temperature and the energy storage within the grout and the outer soil material are presented. The results show that the energy storage in the grout material reaches 62 MJ at the end of 1000 h of ground heat exchanger charging operation, while the energy storage in the surrounding soil can be as high as 7366 MJ. This study also investigates the effect of mass flow rate on the heat transfer performance of the ground heat exchanger. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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37 pages, 412 KiB

Open AccessArticle

Introducing the Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations—II: Illustrative Application to Heat and Energy Transfer in the Nordheim–Fuchs Phenomenological Model for Reactor Safety

by Dan Gabriel Cacuci

Processes 2024, 12(12), 2755; https://doi.org/10.3390/pr12122755 - 4 Dec 2024

Cited by 2 | Viewed by 761

Abstract

This work presents an illustrative application of the newly developed “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)” methodology to determine most efficiently the exact expressions of the first- and second-order sensitivities of NODE decoder responses to the neural [...] Read more.

This work presents an illustrative application of the newly developed “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)” methodology to determine most efficiently the exact expressions of the first- and second-order sensitivities of NODE decoder responses to the neural net’s underlying parameters (weights and initial conditions). The application of the 2nd-FASAM-NODE methodology will be illustrated using the Nordheim–Fuchs phenomenological model for reactor safety, which describes a short-time self-limiting power transient in a nuclear reactor system having a negative temperature coefficient in which a large amount of reactivity is suddenly inserted. The representative model responses that will be analyzed in this work include the model’s time-dependent total energy released, neutron flux, temperature and thermal conductivity. The 2nd-FASAM-NODE methodology yields the exact expressions of the first-order sensitivities of these decoder responses with respect to the underlying uncertain model parameters and initial conditions, requiring just a single large-scale computation per response. Furthermore, the 2nd-FASAM-NODE methodology yields the exact expressions of the second-order sensitivities of a model response requiring as few large-scale computations as there are features/functions of model parameters, thereby demonstrating its unsurpassed efficiency for performing sensitivity analysis of NODE nets. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

23 pages, 334 KiB

Open AccessArticle

Introducing the Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations—I: Mathematical Framework

by Dan Gabriel Cacuci

Processes 2024, 12(12), 2660; https://doi.org/10.3390/pr12122660 - 25 Nov 2024

Cited by 2 | Viewed by 753

Abstract

This work introduces the mathematical framework of the novel “First-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations” (1st-FASAM-NODE). The 1st-FASAM-NODE methodology produces and computes most efficiently the exact expressions of all of the first-order sensitivities of NODE-decoder responses with respect [...] Read more.

This work introduces the mathematical framework of the novel “First-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations” (1st-FASAM-NODE). The 1st-FASAM-NODE methodology produces and computes most efficiently the exact expressions of all of the first-order sensitivities of NODE-decoder responses with respect to the parameters underlying the NODE’s decoder, hidden layers, and encoder, after having optimized the NODE-net to represent the physical system under consideration. Building on the 1st-FASAM-NODE, this work subsequently introduces the mathematical framework of the novel “Second-Order Features Adjoint Sensitivity Analysis Methodology for Neural Ordinary Differential Equations (2nd-FASAM-NODE)”. The 2nd-FASAM-NODE methodology efficiently computes the exact expressions of the second-order sensitivities of NODE decoder responses with respect to the NODE parameters. Since the physical system modeled by the NODE-net necessarily comprises imprecisely known parameters that stem from measurements and/or computations subject to uncertainties, the availability of the first- and second-order sensitivities of decoder responses to the parameters underlying the NODE-net is essential for performing sensitivity analysis and quantifying the uncertainties induced in the NODE-decoder responses by uncertainties in the underlying uncertain NODE-parameters. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

10 pages, 23105 KiB

Open AccessArticle

Ex Ante Construction of Flow Pattern Maps for Pulsating Heat Pipes

by Ali Ahmed Alqahtani and Volfango Bertola

Processes 2024, 12(11), 2585; https://doi.org/10.3390/pr12112585 - 18 Nov 2024

Viewed by 851

Abstract

A novel methodology is proposed for the development of empirical flow pattern maps for pulsating heat pipes (PHPs), which relies on the concept of virtual superficial velocity of the liquid and vapour phases. The virtual superficial velocity of each phase is defined using [...] Read more.

A novel methodology is proposed for the development of empirical flow pattern maps for pulsating heat pipes (PHPs), which relies on the concept of virtual superficial velocity of the liquid and vapour phases. The virtual superficial velocity of each phase is defined using solely the design and operational parameters of the pulsating heat pipe, allowing the resulting flow pattern map to serve as a predictive instrument. This contrasts with existing flow pattern maps that necessitate direct measurements of temperatures and/or velocities within one or more channels of the pulsating heat pipe. Specifically, the virtual superficial velocities are derived from the relative significance of the driving forces and the resistances encountered by each phase during flow. The proposed methodology is validated using flow visualisation datasets obtained from two separate experimental campaigns conducted on flat-plate polypropylene pulsating heat pipe prototypes featuring transparent walls and meandering channels with three turns, five turns, seven turns, and eleven turns, respectively. The PHP prototypes were tested for gravity levels ranging between 0 g and 1 g and heat inputs ranging from 5 W to 35 W. The proposed approach enables the identification of empirical boundaries for flow pattern transitions as well as the establishment of an empirical criterion for start-up. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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27 pages, 8454 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Comparative Techno-Economic Analysis of Parabolic Trough and Linear Fresnel Collectors with Evacuated and Non-Evacuated Receiver Tubes in Different Geographical Regions

by Mehdi Shokrnia, Mattia Cagnoli, Roberto Grena, Antonio D’Angelo, Michela Lanchi and Roberto Zanino

Processes 2024, 12(11), 2376; https://doi.org/10.3390/pr12112376 - 29 Oct 2024

Cited by 2 | Viewed by 1846

Abstract

In the context of Concentrated Solar Power (CSP) technology, this paper presents a comparison between the Parabolic Trough Collector (PTC) and the Linear Fresnel Collector (LFC), considering both evacuated and non-evacuated receiver tubes. The comparison was carried out in terms of the Levelized [...] Read more.

In the context of Concentrated Solar Power (CSP) technology, this paper presents a comparison between the Parabolic Trough Collector (PTC) and the Linear Fresnel Collector (LFC), considering both evacuated and non-evacuated receiver tubes. The comparison was carried out in terms of the Levelized Cost of Electricity (LCOE) considering a reference year and four locations in the world, characterized by different levels of direct normal irradiation (DNI) from 2183 kWh/m²/year to 3409 kWh/m²/year. The LCOE depends on economic parameters and on the net energy generated by a plant on an annual basis. The latter was determined by a steady-state 1D model that solved the energy balance along the receiver axis. This model required computing the incident solar power and heat losses. While the solar power was calculated by an optical ray-tracing model, heat losses were computed by a lumped-parameter model developed along the radial direction of the tube. Since the LFC adopted a secondary concentrator, no conventional correlation was applicable for the convective heat transfer from the glass cover to the environment. Therefore, a 2D steady-state CFD model was also developed to investigate this phenomenon. The results showed that the PTC could generate a higher net annual energy compared to the LFC due to a better optical performance ensured by the parabolic solar collector. Nevertheless, the difference between the PTC and the LFC was lower in the non-evacuated tubes because of lower heat losses from the LFC receiver tube. The economic analysis revealed that the PTC with the evacuated tube also achieved the lowest LCOE, since the higher cost with respect to both the LFC system and the non-evacuated PTC was compensated by the higher net energy yield. However, the non-evacuated LFC demonstrated a slightly lower LCOE compared to the non-evacuated PTC since the lower capital cost of the non-evacuated LFC outweighed its lower net annual energy yield. Finally, a sensitivity analysis was conducted to assess the impact on the LCOE of the annual optical efficiency and of the economic parameters. This study introduces key technical parameters in LFC technology requiring improvement to achieve the level of productivity of the PTC from a techno-economic viewpoint, and consequently, to fill the gap between the two technologies. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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14 pages, 5197 KiB

Open AccessArticle

Numerical Modeling and Experimental Validation of Icing Phenomena on the External Surface of a U-Bend Tube

by Shehryar Ishaque, Sana ur Rehman and Man-Hoe Kim

Processes 2024, 12(11), 2366; https://doi.org/10.3390/pr12112366 - 28 Oct 2024

Viewed by 990

Abstract

The regasification of liquefied natural gas (LNG) is a crucial process that involves certain challenges created by the low temperature of LNG and the risk of ice formation on the external surfaces of the tubes of heat exchangers, which can hinder heat transfer [...] Read more.

The regasification of liquefied natural gas (LNG) is a crucial process that involves certain challenges created by the low temperature of LNG and the risk of ice formation on the external surfaces of the tubes of heat exchangers, which can hinder heat transfer and increase flow resistance. This study presents a numerical model for ice formation on the external surface of the U-bend tube of shell-and-tube heat exchangers. The numerical model has been further enhanced by applying a custom user-defined function. The numerical results were validated using experimental data and demonstrated excellent predictive capability, particularly for the surface temperature of the tubes and the thickness of the ice layer. Hence, this model can reliably capture the overall behavior of the ice formation on the external surfaces of the tubes of shell-and-tube heat exchangers. By highlighting the importance of maintaining stable heat transfer conditions to prevent freezing, this study offers valuable insights that can guide the optimization of heat exchanger designs for LNG regasification. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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Review

Jump to: Research

36 pages, 3503 KiB

Open AccessReview

Production of Biodiesel from Industrial Sludge: Recent Progress, Challenges, Perspective

by Yashar Aryanfar, Ali Keçebaş, Arash Nourbakhsh Sadabad, Jorge Luis García Alcaraz, Julio Blanco Fernandez and Wei Wu

Processes 2024, 12(11), 2517; https://doi.org/10.3390/pr12112517 - 12 Nov 2024

Cited by 5 | Viewed by 2506

Abstract

This study investigated biodiesel production from industrial sludge, focusing on the feasibility and sustainability of converting waste materials into renewable energy sources. This study combines a comparative analysis of various sludge-based biodiesel production methods, highlighting both their environmental benefits and economic potential. Utilizing [...] Read more.

This study investigated biodiesel production from industrial sludge, focusing on the feasibility and sustainability of converting waste materials into renewable energy sources. This study combines a comparative analysis of various sludge-based biodiesel production methods, highlighting both their environmental benefits and economic potential. Utilizing physical, chemical, and biological pre-treatments, this study optimizes biodiesel yield while assessing the impact of each method on the overall production efficiency. Key findings revealed that industrial sludge provides a viable feedstock, contributes to waste reduction, and reduces greenhouse gas emissions. The novel contributions of this study include a detailed economic assessment of biodiesel production from sludge and a comprehensive environmental impact evaluation that quantifies the potential sustainability benefits. Limitations related to scale-up processes are identified, and solutions to overcome these issues are discussed to improve industrial feasibility. Furthermore, the integration of sludge-based biodiesel production with other renewable energy systems has been explored as a future avenue to enhance energy efficiency and sustainability. This research contributes to a significant scientific niche by addressing scalability challenges and proposing future perspectives for sustainable biodiesel production from industrial waste. Full article

(This article belongs to the Special Issue Heat and Mass Transfer Phenomena in Energy Systems)

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